1. Field of the Invention
The present invention relates to a data shared system using a plurality of processing units and data storage units in a storage area network.
2. Description of the Prior Art
Introduction to Fibre Channel
Fibre Channel is an American National Standards Institute interface including SCSI-3, HIPPI-FP, IP and ATM/AAL5. Fibre Channel Arbitrated Loop is one topology used to connect two or more devices within the guidelines by ANSI standard.
Fibre Channel supports both large and small data transfers with the feature of separating the physical I/O interface from the I/O operation.
It can support both channel and network peripheral protocols for device communication. This means that channel and network protocols can share the same physical medium.
Fibre Channel does not have its own native I/O command set protocol. It simply lets other protocol superimpose their command sets onto itself and then transports this information with very high bandwidth over 100 M bytes per second.
Fibre Channel systems take on three topologies: point to point, arbitrated loop and switched fabric. Point-to-point connections are paths between two nodes in a network. Fibre channel arbitrated Loop (FC-AL) consists of multiple nodes chained from a system. Third one is switched design that allows huge number of nodes to be connected through switches.
Fibre Channel connectivity is accomplished in much the same way that today""s local area networks (LAN) are assembled. Network interface cards should be installed to each node and connected via physical cabling. To build networks, arbitrated loop hubs and fabric switches are used.
One of the most attractive features of Fibre Channel is that it merges the channel and the networking paths. Due to its generic transport capability, Fibre Channel can carry channel traffic such as SCSI or HIPPI as well as Ethernet over the same physical connection.
Before Fibre Channel, two distinct paths existed in the LAN for sending information. The first is the network and the second is channel (storage bus). Networks consist of much more random communication than do channels. Network protocols establish the rule (protocol) by which the network sends and receives data. As a result, networks have high overhead.
On the contrary, channels perform a very straightforward task, sending and receiving data. Therefore, channel performance is much higher than networks, but channel can not handle sophisticated task like file protocol handling.
Fibre channel has both of network and channel capability, so there is a possibility to have both sophisticated protocol and channel level performance. But current technology does not have the solution how to merge sophisticated protocols into channel interface.
Introduction to SAN (Storage Area Network)
Storage Area Network uses typically channel paths to get high performance interconnected shared storage environment. SAN is another network constructed from local interconnects such as SCSI, Escon and Fibre Channel. SAN is a new way of attaching storage units to the Network. SAN enables the storage unit to be separated from the server and enables the storage unit to be shared among multiple servers.
LAN comprises network traffic, whereas the SAN interconnects channel paths. LAN protocols offer a feasible solution for creating networks of storage units. On the other hand, SAN is very suitable for storage sharing with multiple servers by very high performance. But SAN does not provide feasible solution for networks, because channel interface does not provide network protocols.
The problem with early stage of SAN is that servers can not actually share the data on the storage while the storage is to be said shared among the several servers. So the first stage of SAN OS provided volume-level locking mechanism in order to solve the problem. But its performance is not good, not drawing out potential SAN performance.
Volume-level locking is to lock the entire HDD or a partition of HDD in order to share the data of HDD. This method is very primitive, because the unity of the lock is physical unit of HDD. The granularity is not fine, so the performance of volume-level locking is not good.
In the second stage, SAN OS provided file-level locking mechanism in order to solve both of the problems. But still they have a problem. That is the second stage SAN OS requires other servers to access storage through a single server that handles locking mechanism. This creates potential bottlenecks and single point of failure.
File-level locking mechanism is to lock each file to use. This method depends on the logical structure of data. The granularity of lock level is fairly fine, so the users can get good performance through file-level locking mechanism.
According to the present invention, there is provided a shared file apparatus accessed via a network, in which a plurality of protocols are usable, by a plurality of file processing apparatuses interconnected by the network, the shared file apparatus comprising:
a first acceptor for accepting a file lock request from the file processing apparatuses by use of a first protocol;
a sender for sending a file access allowance to one of the file processing apparatuses upon receipt of the file lock request; and
a second acceptor for accepting a file access command from the file processing apparatus by use of a second protocol to which the file access allowance is sent.
Also, according to the present invention, there is provided a shared file apparatus accessed via a network, in which both a Network Protocol and a Storage Protocol are usable, by a plurality of file processing apparatuses interconnected by the network, the shared file apparatus comprising:
a first acceptor for accepting a file lock request from the file processing apparatuses by use of the Network Protocol;
a sender for sending a file access allowance to one of the file processing apparatuses upon receipt of the file lock request; and
a second acceptor for accepting a file access command from the file processing apparatus by use of the Storage Protocol to which the file access allowance is sent.
Moreover, according to the present invention, there is provided a method of sharing a file accessed via a network, in which a plurality of protocols are usable, by a plurality of file processing apparatuses interconnected by the network, the method comprising:
accepting a file lock request from the file processing apparatuses by use of a first protocol;
sending a file access allowance to one of the file processing apparatuses; and
accepting a file access command from the file processing apparatus by use of a second protocol to which the file access allowance is sent.
Further, according to the present invention, there is provided a computer-readable storage medium having a program recorded thereon;
where the program is to make the computer execute a method of sharing a file accessed via a network, in which a plurality of protocols are usable, by a plurality of file processing apparatuses interconnected by the network, the method comprising:
accepting a file lock request from the file processing apparatuses by use of a first protocol;
sending a file access allowance to one of the file processing apparatuses; and
accepting a file access command from the file processing apparatus by use of a second protocol to which the file access allowance is sent.
Furthermore, according to the present invention, there is provided a file processing apparatus for accessing a shared file apparatus connected to a network in which a plurality of protocols are usable via the network, the file processing apparatus comprising:
a first sender for sending a file lock request to the shared file apparatus by use of a first protocol;
an acceptor for accepting a file access allowance from the shared file apparatus to which the file lock request is sent; and
a second sender for sending a file access command to the shared file apparatus by use of a second protocol upon receipt of the file access allowance.
Also, according to the present invention, there is provided a file processing method for accessing a shared file apparatus connected to a network, in which a plurality of protocols are usable, via the network, the method comprising:
sending a file lock request to the shared file apparatus by use of a first protocol;
accepting a file access allowance from the shared file apparatus to which the file lock request is sent; and
sending a file access command to the shared file apparatus by use of a second protocol upon receipt of said file access allowance.
Moreover, according to the present invention, there is provided a computer-readable storage medium having a program recorded thereon;
where the program is to make the computer execute a file processing method for accessing a shared file apparatus connected to a network, in which a plurality of protocols are usable, via the network, the method comprising:
sending a file lock request to the shared file apparatus by use of a first protocol;
accepting a file access allowance from the shared file apparatus to which the file lock request is sent; and
sending a file access command to the shared file apparatus by use of a second protocol upon receipt of said file access allowance.